In the wake of news that the U.S. military bombed forces allied with the Syrian government of President Bashar al-Assad on Thursday, at least one member of Congress is voicing dissent by saying President Donald Trump has no legal authority to order such attacks.

"For the second time in as many months, the U.S. military has conducted airstrikes against pro-Assad forces in Syria," said Rep. Ted Lieu (D-Calif.). "The Trump Administration does not have congressional authorization to carry out military strikes against the Assad regime. Furthermore, the situation that led to today's strike is precisely why I warned against getting further entangled in the Syrian civil war without a clear strategy."

In a previous tweet, Lieu called the bombing "frickin' illegal."

If true, this is FRICKIN ILLEGAL. Trump does not have Congressional authorization to attack Syria, a country that has not attacked US. https://t.co/5cf7gBVwC7

Phyllis Bennis, director of the New Internationalism Project at the Institute for Policy Studies, thinks the congressman is right on target.

"Rep. Lieu is absolutely right," Bennis told Common Dreams in an email, "today’s airstrikes against Syrian government forces were 'frickin’ illegal.' They violate both international and US domestic law."

It's important to note, Bennis added, that is violation is nothing this is nothing new when it comes to U.S. policy.

"The entire U.S. military operation in Syria is violating domestic and international law," she explained. "Internationally, the use of military force by one nation against another country is only legal if it's approved by the UN Security Council, which this wasn't, or in case of immediate self-defense if an armed attack occurs, which it didn't. Under U.S. law, the War Powers Act governs if and when a president can send troops into harms way—and that's actually a pretty high bar. Only if Congress declares war, which they didn't (and in fact haven’t since World War II), or if Congress authorizes the attack, which they didn't, or in immediate response to a military attack."

Based on what's known at this point, said Bennis, none of those criteria were met in this case. Even though everyone knows that U.S. troops are operating inside Syria, she explained, they are not there in a sanctioned or legal way. "So even a threatened attack on them does not make their presence or airstrikes to support them legal," she argued.

According to statements from U.S. officials to various newsoutlets, Thursday's bombing by U.S. forces took place near the town of al-Tanf, inside the so-called "deconfliction zone" in the south near the border with Iraq and Jordan. Reporters were told the airstrike was conducted because militia forces allied with the Syrian army and backed by Iran were moving towards rebel groups backed by the United States.

With U.S. Special Forces actively training anti-Assad rebels at a military base near al-Tanf, that is the likely reference of U.S. "entanglement" made by Lieu in his statement. And while both Trump and President Barack Obama before him have relied on the Authorization of Military Force (AUMF) decrees approved by Congress in the wake of the attacks on September 11, 2001, few legal or military experts believe that authorization should apply to fighting against anyone the president determines is an enemy.

"Claiming reliance on the worn-out and over-used AUMF passed immediately after the 9/11 attacks should be explicitly rejected," said Bennis. "That AUMF was limited to authorizing attacks on those who perpetrated the 9/11 attacks and those who support them – meaning al Qaeda and the Taliban. Period, full stop. Claiming that that moldy 16-year-old document somehow also allows the president to order attacks on organizations like ISIS that didn’t even exist in 2001 and that are in fact fighting against al Qaeda, let alone allowing attacks on the military forces of a government, however brutal in its own country, that the US has not declared war on, is simply unacceptable."

Along with other lawmakers and Middle East experts who have repeatedly warned against escalation in Syria, or the foolishness of further injecting the U.S. military into the nation's brutal and protracted civil war, Lieu said that Trump must make clear his intentions regarding Syria. In April, critics slammed Trump for launching a cruise missile attack on a Syrian air base after exposure to chemical agents killed dozens of civilians near the northern town of Idlib.

According to Lieu on Thursday, "President Trump needs to explain his plan for Syria to Congress and the American people."

For her part, Bennis believes that it's past time for other members of Congress to take a tougher stance when it comes to war-making.

"Congress can no longer sit on its hands and allow this administration or any other to send US military power—troops, planes, bombs, airstrikes, drones and more—against people and countries across the globe without its permission," Bennis concluded. "Congress must be held accountable to enforce its own powers – no one else will."